1. Field of the Invention
The present invention relates generally to the field of electrical interconnection (contact) elements, and, more particularly, to interconnection elements and tip structures suitable for effecting pressure connections between electronic components.
2. Description of the Related Art
Generally, interconnections between electronic components can be classified into the two broad categories of “relatively permanent” and “readily demountable”. An example of a relatively permanent connection is a solder joint. Once two electronic components are soldered to one another, a process of unsoldering must be used to separate the components. A wire bond, such as between a semiconductor die and the inner leads of a semiconductor package (or the inner ends of lead frame fingers) is another example of a relatively permanent connection.
One example of a readily demountable connection is rigid pins of one electronic component being received by resilient socket elements of another electronic component. The socket elements exert a contact force (pressure) on the pins in an amount sufficient to ensure a reliable electrical connection therebetween. Another type of readily demountable connection are interconnection elements (also referred to herein as springs, spring elements, spring contacts or spring contact elements) that are themselves resilient, springy, or mounted in and/or on a spring medium. An example of such a spring contact element is a needle of a probe card component. Such spring contact elements are typically intended to effect temporary pressure connections between a component to which they are mounted and terminals of another component, such as a semiconductor device under test.
Tip structures are often mounted (or affixed or coupled) to one end of an interconnection element. Tip structures provide a desired tip shape to the interconnection elements and are particularly useful in providing a small area contact with a controlled geometry that creates a repeatable high pressure. Tip structures become increasingly critical as the interconnection elements themselves become smaller and smaller. A tip structure may also have topological features on its surface to assist in providing an electrical contact between the two electrical components. For example, the purpose of the tip structure is typically to break through the nonconductive layer (often corrosion, oxidation products, or other types of contaminated films) on the terminals of the electrical component under test. As a contact force is applied, the interconnection element applies a pressure to the terminal of the electronic component under test and causes the tip structure to deflect across the terminal. This small horizontal movement of the tip structure across the surface of the corresponding terminal allows the tip structure to penetrate the nonconductive layer on the terminal, thereby establishing a good electrical contact between the two electronic components. For example, tip structure 10 mounted to interconnection element 12 (shown in FIGS. 1A and 1B) has a blade 14 that scrapes aside the non-conductive layer in order to achieve an electrical contact.
There are a number of problems associated with achieving the above-described electrical contact. First, as the terminal contact areas also get smaller, the horizontal movement of the tip structure 10 becomes an issue. Second, as the tip structure 10 is forced to deflect across the terminal (see FIG. 1B), it may also be forced down and away from the terminal causing the blade 14 of the tip structure 10 to rotate away from the terminal as the tip structure 10 deflects across the terminal. The rotation of the blade 14 away from the terminal of the electronic component under test reduces the chances of the tip structure achieving a dependable electrical contact with the terminal of the electronic component. Further, as the tip structure scrapes across the non-conductive surface of the terminal in an effort to penetrate the nonconductive surface and establish a good electrical contact, stray particles and buildup often occur along the blade 14 and upper surface of the tip structure 10. This buildup may contribute to high contact resistance between the tip structure and the terminal, which may cause inaccurate voltage levels during device testing due to the voltage produced across the tip structure. The inaccurate voltage levels may cause a device to incorrectly fail, resulting in lower test yields when the contact is used in a device testing environment.
Thus, an interconnection element and tip structure that minimize buildup along the blade of the tip structure and maximize contact pressure between the tip structure and the terminal of the electronic component under test as the tip structure deflects across the surface of the terminal is desired.